It has previously been proposed to control the braking effort applied to various brakes in a multi-axle vehicle--see the referenced U.S. Pat. No. 4,606,586, PCT Publication WO No. 83/03230. The publication describes a system in which the loading of the axles is separately determined and control signals are derived from this determination to then, in turn, control the distribution of braking effort at the respective wheels of the respective axles.
The system requires separate determination of loading at the respective axles, which requires a multiplicity of sensors.